NED Abstract

Copyright by American Astronomical Society.
Reproduced by permission
1996ApJ...460..271K
MOLECULAR GAS IN ELLIPTICAL GALAXIES: CO OBSERVATIONS OF AN IRAS
FLUX-LIMITED SAMPLE
G. R. KNAPP
Department of Astrophysical Sciences, Princeton University,
Princeton, NJ 08544;
gk@astro.princeton.edu
AND
M. P. RUPEN
National Radio Astronomy Observatory, P.O. Box 0, Socorro, NM 87801;
mrupen@aoc.nrao.edu
Received 1995 July 27; accepted 1995 September 20
ABSTRACT
A search for CO(2-1) emission from 42 early-type galaxies with 100
micron flux densities greater than 1 Jy detected (tentatively in some
cases) 11 galaxies and tentatively found absorption against the active
nucleus in two. Data from this survey and from the literature show that
the overall detection rate of CO emission or absorption in elliptical
galaxies is 45% and that the detection rate increases with increasing 100
micron flux density. The data suggest that all elliptical galaxies
contain a small amount of cold interstellar matter.
The CO and far-infrared fluxes are well correlated, though the
relationship shows a lot of scatter, which does not appear to be caused
by variations in the temperature of the interstellar dust and probably
indicates differences in the physical state of the interstellar medium
from galaxy to galaxy. The CO flux densities are completely uncorrelated
with the galactic starlight.
The detection of CO emission shows that many elliptical galaxies have
dense cold gas in their inner regions. The four galaxies which are known
to have CO absorption, including the two from the present paper, have
relatively narrow absorption components which are at the galaxy's
systemic velocity and/or redshifted with respect to this velocity,
consistent with infall to the center of the galaxy.
Subject headings: galaxies: elliptical and lenticular, cD - galaxies: ISM
- infrared: galaxies - ISM: molecules